The proposal outlines a research plan for David Wu, MD PhD, to perform postdoctoral training in the laboratories of Gokhan Mutlu, MD, and Yun Fang, PhD, for two years. The ultimate goal of this research project is to make discoveries in vascular biology that could be useful in promoting human health; another goal is to be- come fluent in the basic techniques in cellular and molecular biology, and ultimately to jump start a research program for the eventual application of a K-level award in vascular biology. During the 2 year mentored period, Dr. Wu will receive additional academic and scientific guidance from the mentors and an advisory committee at the University of Chicago. The overall research goal is to determine the role that shear stress plays on endothelial cell (EC) metabolism, which plays a fundamental role in endothelial activation. Endothelial activation is the process by which ECs have reduced barrier function and increased inflammation. That endothelial activation occurs with a significant upregulation of glycolysis is a recently discovered phenomenon. That low shear stress generated by ?atheroprone? blood flow (as opposed to high shear stress during normal, ?atheroprotective? blood flow) is important in determining endothelial activation is also well-described. However, how changes in shear stress produce changes in the metabolism of ECs is unknown. Dr. Wu now has confirmatory data that human aortic endothelial cells (HAECs) exposed to atheroprone flow upregulate key enzymes in glycolysis, angiogenesis, and inflammation. Dr. Wu also has preliminary data that suggests HAECs are unable to use their mitochondria to generate energy under atheroprone flow. Excitingly, he recently found that atheroprone flow led to normoxic stabilization of transcription factor hypoxia inducible factor-1? (HIF-1?), which is known to upregulate glycolysis in many other contexts. This is counterintuitive, as HIF-1? activity is thought to be suppressed in high oxygen tension settings, such as in arterial blood flow. Furthermore, Dr. Wu found that lysophosphatidic acid (LPA) signaling, increased in atheroprone flow (and working through RhoA and Rac1, small GTPases which modulate cytoskeletal organization), and also known to be a key mediator of atherosclerosis, also induces HIF-1?. Collectively, these results led to his central hypothesis: atheroprone flow-mediated modulation of LPA signaling through RhoA or Rac1 leads to metabolic changes in a HIF-1? dependent manner. Aim 1 will test the hypothesis that HIF-1? stabilization is required for upregulation of glycolysis, mitochondrial insufficiency, and EC activation under atheroprone flow. Aim 2 will test the hypothesis that atheroprone flow stabilizes HIF-1? through LPA signaling via RhoA and Rac1. The goal is to achieve a mechanistic understanding of shear-stress related changes in metabolism. Endothelial activation occurs naturally in atheroprone flow states (near valves and arterial branch points) ? this results in chronic inflammation and ultimately atherosclerosis, a leading cause of morbidity and mortality in the United States. Thus, there is a significant need to better understand how shear stress induces metabolic changes and hence EC activation.